1. Field of the Invention
The present invention is directed to polyisocyanates and in particular to polyisocyanates useful in elastomeric coatings.
2. Description of the Prior Art
Elastomeric coating compositions are often used to form a protective coating on a substrate. In many cases, the composition forms a protective coating on roofs, or a substrate provided by one or more components of an automotive vehicle.
U.S. Pat. No. 6,613,389 discloses elastomeric coating compositions that include at least two components, a polyisocyanate component; and an amine component.
U.S. Pat. No. 6,733,838 discloses fluorinated polyurethane elastomer coatings prepared by the reaction of a polyol in a base component with a polyisocyanate in the curing agent.
Many elastomeric coatings utilize aliphatic polyisocyanates containing uretdione groups with low NCO functionality because of their desirably low viscosity. However, the uretdione structure can be prone to scission under high temperatures or aging, reforming monomeric isocyanates and liberating carbon dioxide. This causes many problems within the coating, including blistering and lower tensile strength.
There is therefore a need in the art for elastomeric coating compositions that do not degrade when exposed to high temperatures and/or aging.